I'm curious to see what Valve comes up with. I don't think there's much you can change in regards to 'basic input'. The keyboard is a great invention. Just because it hasn't changed doesn't mean it should. The mouse could use a little overhaul. They could maybe add a trackball on top instead of a scroll wheel. That would be the one thing I would change and I'm sure someone has tried that already.
In any case, I don't feel a void when it comes to new hardware for gaming. Game consoles have been trying new interactive devices for the last system incarnations and they've failed. I have yet to try a motion control system that felt flawless and honestly, necessary.
I believe we've come to a great point in PC gaming where the video card is the only thing you need to add to a system to make it worth it. If anything, the software needs to be better and more compelling.